Anti-intrusion alarm system

ABSTRACT

An anti-intrusion alarm system includes a source of power, a normally open, motion-sensitive switch remotely located with respect to said power source, a normally conducting circuit interrupting means located adjacent the power source, such as, the contacts of a relay, holding means operatively associated with the circuit interrupting means, located adjacent said power source and adapted to render the circuit interrupting means nonconducting, such as, the coil of the relay, an alarm means, a first alarm circuit connecting the alarm to the power source through the motion-sensitive switch, whereby the closing of the motion-sensitive switch energizes the alarm, a second alarm circuit connecting the alarm to the power source through the circuit interrupting means, and a third circuit connecting the holding means to the power source through the remote location adjacent the motion-sensitive switch, whereby the interruption of power between the power source and the holding means inactivates the holding means and permits the circuit interrupting means to conduct power from the power source through the alarm.

United States Patent 1 Klebold et al.

[ l ANTl-lNTRUSlON ALARM SYSTEM [76] Inventors: Franklin R. Klebold,4103 E.

Belknap; Robert L. Bruce, 1604, both of Fort Worth, Tex. 76111 [22]Filed: Oct. 6, 1972 [21] Appl. No.1 295,436

[52] US. Cl. 340/261; ZOO/61.49; 340/276; 340/409 [51] Int. Cl. G08b13/02 [58] Field of Search 340/409, 280, 261, 214, 340/256, 253 B, 283,276, 63, 65; 200/61.49

[56] References Cited UNITED STATES PATENTS 1,494,656 5/1924 Wherland340/276 1,920,742 8/1933 Chapman... 340/276 2,270,274 l/1942 Davis340/276 X 2,402.111 6/1946 Engler 200/61.49 2,407,122 8/1946 Young200/61.49 2,686,909 8/1954 Poulson 340/256 X 2,874,376 2/1959 Spenard340/276 2,944,251 7/1960 Tetherow.... 340/409 3,053,949 9/1962 JohnsonZOO/61.49 3,103,003 9/1963 Roberts 340/214 X 3,150,359 9/1964 Hoey340/214 X 3,176,283 3/1965 Shanahan.... 340/409 3,448,447 6/1969Tetherow 340/409 3,550,120 12/1970 Kompelin 340/409 3,594,771 7/1971Uthene 340/276 3,597,753 8/1971 Tabankin 340/261 X 1 Dec.2,1975

Primary Examiner-Glen R. Swann, lll Attorney, Agent, or Firm-Charles F.Steininger [5 7] ABSTRACT An anti-intrusion alarm system includes asource of power, a normally open, motion-sensitive switch remotelylocated with respect to said power source, a normally conducting circuitinterrupting means located adjacent the power source, such as, thecontacts of a relay, holding means operatively associated with thecircuit interrupting means, located adjacent said power source andadapted to render the circuit interrupting means nonconducting, such as,the coil of the relay, an alarm'means, a first alarm circuit connectingthe alarm to the power source through the motionsensitive switch,whereby the closing of the motionsensitive switch energizes the alarm, asecond alarm circuit connecting the alarm to the power source throughthe circuit interrupting means, and a third circuit connecting theholding means to the power source through the remote location adjacentthe motion-sensitive switch, whereby the interruption of power betweenthe power source and the holding means inactivates the holding means andpermits the circuit interrupting means to conduct power from the powersource through the alarm.

15 Claims, 4 Drawing Figures US. Patent Dec. 2, 1975 Sheet 1 of33,924,254

US. Patent Dec. 2, 1975 Sheet 2 of3 3,924,254

NQ-n- ANTI-INTRUSION ALARM SYSTEM The present invention relates to ananti-intrusion alarm system. In a more particular aspect, the presentinvention relates to an anti-intrusion alarm system which is eithernormally actuated if a highly-sensitive switch is closed by an intruderor abnormally actuated if a line leading from the switch to the alarmand control portion of the system is cut or broken.

In the prior art, a wide variety of anti-intrusion alarm systems havebeen developed. For themost part, these systems are rather complex andexpensive to install and maintain. One reason for the expense andcomplexity of such alarm systems is that several sources of power arerequired and quite often, several individual alarms are required. A

Electrical alarm systems are generally of two types. In one type, anormally open circuit is closed in the alarm condition, and, in theother type, a nonnally closed circuit is opened in the alarm condition.The alarm condition is generally initiated by an intruder breaking awire or other filament stretched across the area to be protected. Thus,in these types of devices, there is only one condition which will createthe alarm condition.

On the other hand, systems have also beendeveloped which include ananti-intrusion circuit operated by a switch or the breaking of a wire orfilament and an antitampering section which sets off an alarm to theextent that a line leading from the protected area to' the alarm andcontrol area is broken or tampered with. However, in systems of thistype, two separate power supplies are generally required, one to operatethe normal switch or filament operated anti-intrusion section and aseparate and distinct power supply to operate the anti-tamperingsection. Thus, these systems become unduly complex and expensive to theextent that they are in essence separate and distinct alarm systems, andthere is really little or no connection between the two.

It is therefore an object of the present invention 'to provide animproved anti-intrusion alarm system. Another object of the presentinvention is to provide an improved anti-intrusion alarm system which issimple, inexpensive and readily installed. Yet another object of thepresent invention is to provide an improved antiintrusion alarm systemincluding a highly-sensitive, motion-actuated switch. Still anotherobject of the present invention is to provide an improved anti-intrusionalarm system normally actuated by the closing of a switch and abnormallyactuated by cutting an electrical connection between the switch and thealarm system proper. Another and further object of the present inventionis to provide an improved anti-intrusion alarm system which requires asingle power source for both normal operation of the alarm by anintruder and abnormal operation of the alarm by cutting the electricalconnection between an intruder-operated switch and the alarm and controlportion of the system. 1

These and other objects and advantages of the present invention will beapparent from the following detailed description when read inconjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an exploded isometric viewof the two major components of the alarm system,

FIG. 2 is .an electrical schematic of the alarm system; FIG. 3 is anelectrical schematic of a solid state modification of the circuit ofFIG. 2; and

FIG. 4 is an isometric view of a single unit embodying V the alarmsystem.

SUMMARY OF THE INVENTION vated by the power source when an intrudercloses the contacts in the switch in a first alarm circuit and anormally open second alarm circuit connects the alarm .to the powersource when a line between the power source and the alarm is cut, brokenor disconnected.

DETAILED DESCRIPTION OF THE INVENTION In accordance with FIG. 1 of thedrawings, the alarm system of the present invention is made up of twobasic units, namely; switch or sensor unit 10 and the alarm or controlunit 12. Units 10-and 12 are connected by a amp, three conductor line14. 1

Switch or sensor unit 10 is made up of a base 16 and a cover 18. Mountedon base 16 is a motion-sensitive, vibratory switch or sensor unit. Theswitch or sensor unit is made up of a vertically-disposed ring contact20 having an aperture 22 formed through its center. The other contact ofthe switch comprises a resilient wire, resilient, flat metal arm orother spring-type or resilient arm 24 which is mounted on base 16 at oneend and then passes through aperture 22 of ring contact 20. Mounted onthe free end of arm 24 is a weight 26. The resilience of arm 24 and themass of weight 26 are chosen such that arm 24 is normally balancedwithin the center of aperture 22 of ring contact 20 when the base 16 isin a generally-horizontal position or resting on a flat surface of someform. However, if the switch is disturbed in any manner, the mass ofweight 26 and the resilience of arm 24 will cause the arm 24 to vibrate,thereby momentarily contacting the edges of aperture 22 of ring contact20 and completing a circuit through the switch. Thus, a verticaldisturbance will cause the arm 24 to vibrate vertically, thus causing aplurality of momentary contacts between arm 24 and ring contact 20. Onthe other hand, again because of' the resilience of arm 24 and the massof weight 26 balancing the arm, if the unit 10 is turned on either sideor upside down, arm 24 will be in continuous contact with eitherthesides or top, respectively, of the aperture 22 in ring contact 20,thereby maintaining the switch in a continuously closed condition untilthe state of balance is again attained and maintained by placing theswitch unit 10 in a perfectly horizontal, undisturbed position. Thus, itis obvious from the operation of switch unit 10 that any slightdisturbance of the switch unit will cause at least a momentary closingof the switch, thereby closing the alarm circuit as hereinafterdescribed.

As will also be hereinafter described in greater detail, abreaking orcutting of line 14, connecting sensor unit 10 to control and alarm unit12, will also set off the alarm.

Further in accordance with FIG. 1, the alarm and control unit 12 is madeup of a base or casing 28 and cover plate 30. Mounted in cover plate 30is an indicator light 38 which shows when the system is on. For purposesof testing the various circuits, switches 40 and 3 42 are also mountedin cover panel 30. Switch 40 is designed to test the integrity oroperability of the alarm and control unit 12, whereas switch 42 isdesigned to test the integrity and operability of the switch or sensorunit 10.

Referring now to FIG. 2 of the drawings, the electrical circuit for thealarm system is made up of four basic sections. Specifically, thesesections include section 44 representing the power supply and powerindicator control section, section 46 representing the anti-tampersection and the test sections, section 48 representing the alarm sectionand section 50 representing the detector or sensor section. Aspreviously indicated in the description of FIG. 1, the indicator orsensor section represents one individual unit whereas the remainder ofthe circuit is all included within a second individual unit, and the twounits are connected by a three wire electrical line.

1 Volts AC power is fed to transformer 52 through line 32. The powersupplied to transformer 52 is switched off and on by means of lineswitch 34 which is in series with the primary 54 of transformer 52. Alsoin series with primary 54 of transformer 52 is line fuse 36.

former 52. Transformer 52 is preferably a step-down transformer whichreduces the voltage to a value of about 16 volts AC. Having this lowvoltage operating the alarm system, it is obvious that the detectorsection 50 is completely safe and shockproof.

The anti-intrusion or sensor section 50 includes the motion-sensitiveswitch unit 10 which is remotely located with respect to the remainderof the circuit. The switch unit 10 is, of course, made up of ringcontact 20 and arm contact 24. Power from the secondary 58 oftransformer 52-is supplied to-the switch through line 86, thence throughthe closed contacts 20 and 24 of the switch and from the switch throughline 88 which leads to the alarm section 48. The alarm section 48includes an appropriate multi-vibrator 72 having contacts 74 and coil76. Power from the secondary 58 of the transformer thus passes throughline 86, contacts 20 and 24 of switch 10, line 88, thence to the coiland contacts 76 and 74, respectively, of multi-vibrator 72 and back tothe transformer secondary 58 through line 78. Accordingly, when switch10 is closed either momentarily or continuously by a disturbance createdby an intruder violating the area to be protected, power will besupplied through the switch 10 to the multi-vibrator 72, thus normallyclosing the alarm circuit and setting off the alarm. As previouslyindicated, switch 10 is remotely connected to the remainder of thesystem through a three wire electrical line. Two of these three wirescomprise wires 86 and 88, which were previously referred to. I

The anti-tampering section of the system, specifically section 46,comprises a normally closed switch which is held in its open position bypower being supplied to the switch and which automatically closes whenthe power is interrupted. In a specific instance, as shown, this switchcomprises a normally closed relay 62. The relay 62 can be substitutedfor by an equivalent semiconductor device. In any event, power issupplied to the coil 66 of relay 62 through line 86, line 90 and line92. Thus,

so long as power is being supplied to points 68 and 70 of coil 66 ofrelay 62, the relay will be held in its open position. Contacts 60 and64 of relay 62 are connected to the power source through the alarm orbuzzer 72. Specifically, this circuit includes line 82, contacts 60 and64, line 84, alarm 72 and line 78.' Consequently, if

the power to relay 62 is interrupted for any reason, the

moving contact 64 of relay 62 will be released and close the relaycontacts 60 and 64, thus completing a circuit through the alarm 72.Specicically, if the power to relay 62 is interrupted by cutting orbreaking either line 86 or line 90, the relay contacts will be released,the relay will close and power will be supplied to the buzzer or alarmcircuit, thus indicating that someone has broken or cut the line fromthe sensor switch 10 (FIG. 1) to thecontrol section 12 (FIG. 1). Theswitch unit 50 is conveniently connected to the remainder of the systemby means of single contact jack and plug units 94, 95 and 98. Obviously,if either plug 94 or 98 is pulled, the alarm will indicate suchtampering also. As a matter of convenience, particularly so that line 88cannot be individually disconnected, a single plug can be utilized forjacks 94, 96 and 98.

In order to test the anti-intrusion portion of the circuit, a normallyopen, momentary, single pole, single throw test switch 42 is closed.This bypasses switch 10 and completes a circuit through alarm 72, thussetting off the alarm and checking its operability. Similarly, normallyclosed, momentary, single pole, single throw test switch 40 is opened totest the anti-tampering section and its operability. Opening switch 40will cut off the power to relay coil 66, thus closing relay contacts 60and 64 and completing this circuit through the alarm 72. This, ofcourse, assures that the anti-tampering section is operable and will setoff the alarm if lines 86'or 90 are cut.

In the operation of the alarm system, it becomes quite obvious that anydisturbance of the switch 10 will close contacts 20 and 24 of switch 10at least momentarily. Actually, because of the resilience of arm 24,only a single contact is extremely unlikely or almost impossible sincethe weight on the end of arm 24 will cause the arm to vibrate a numberof times once it is disturbed. In any event, when switch 10 is closed,the secondary 58 of transformer 52 supplies power to the buzzer or alarm72 through lines 86, 88 and 78, thus completing the circuit through thealarm and setting off the alarm or buzzer.

However, aside from the alarm condition which occurs during normaloperation, when switch 10 makes contact, there is another conditionwhich will set off the alarm even without the closing of switch 10.Specifically, as previously indicated, when voltage is lost acrosspoints 68 and 70 of coil 66 of relay 62, the alarm will be set off.Consequently, if either lines 86 or 90 are out between the switch andthe control and alarm section, contacts 60 and 64 of relay 62 willclose, thus supplying power to the alarm 72 through lines 82, 84 and 78,thereby indicating that someone has tampered with the line between theswitch 10 and the alarm section. Such tampering can, of course, alsoinclude the pulling of one of plugs 94, 96 or 98. r

v FIG. 3 of the drawings shows an alternative circuit to that of FIG. 2.FIG. 3 includes the same basic components as the system of FIG. 2 withthe exception that solid state means have been substituted for theelectromechanical components of the system of FIG. 2. Specifically, FIG.3 contains a power supply 102 which is the equivalent of power supply orpower section 44 of FIG. 2.'Also shown in FIG. 3 is the detector orsensor section 104 which is the equivalent of sensor section 50.Anti-tampering section 106 is the equivalent of anti-tampering section46. Finally, alarm or signal section 108 represents the equivalent ofalann or signal section 48.

Power supply or power section 102 is provided with a 12 volt DC battery110. As is obvious, the power section 44 of FIG. 2 could also be used inthe circuit of FIG. 3 as could the power section 102 of FIG. 3 be usedin the circuit of FIG. 2.

Anti-tampering section 106 is made up basically of a holding meansrepresented by PNP transistor 112 and a circuit interrupting meansrepresented by N-type base, field-effect transistor 114. Transistor 112is preferably a Fairchild 2N3638 component while transistor 114 ispreferably a General Electric C106Y component.

Leading from the anti-tampering section 106 to a remotely locateddetector or sensor unit 104 are three conductors; namely, 116, 118 and120. Located within remotely located detector or sensor section 104 is a1.5 volt DC battery 122 which maintains a positive bias on the base oftransistor 112. Located in line 118 is a switch 124, which is themotion-sensitive switch previously discussed and designated as switchnumber in FIG. 2.

Finally, leading from the anti-tampering section 106 are two leads 130and 128 to a suitable alarm means 108. In this specific instance, thealarm means is a warble tone generator which is completelytransistorized. The warble tone generator is connected to an externalspeaker or amplifier and speaker (not shown) through lines 126 and 130.Obviously, warble tone generator 108 can be a 12 volt DC bell, a sirenor the buzzer 72 of FIG. 2. Warble tone generator 108 contains 3 basiccomponents; namely, NPN transistor 132, NPN transistor 134 and NPNtransistor 136. All three transistors are preferably Fairchild 2N2926elements. Transistor 132 plus transistor 134 have a frequency of 700 Hzwhile transistor 132 plus transistor 136 have a frequency of 500 Hz. Theswitching rate of warble tone generator 108 is 1.5 Hz.

The circuit of FIG. 3 operates in basically the same manner as that ofFIG. 2 except for the substitution of solid state elements. The 1.5 voltbias on the base of transistor 112 prevents any appreciable current fromflowing through transistor 112 from the 12 volt power source 110 and,therefore, transistor 114 will be in a non-conducting condition, and thealarm will be inactive. However, if an intruder should actuate themotion-sensitive switch 124 in line 118, this will short out the 1.5volt bias and the full 12 volts'from battery 110 will pass throughtransistor 1 12. With this voltage passing through transistor 112,transistor 114 will conduct, thereby, actuating the alarm 108.Similarly, if lines 120 or 116 between the sensor section 104 and theremainder of the device are cut by an intruder, this will again cut offthe 1.5 volt bias from the base of transistor 112 and power will then besupplied to the base of transistor 114 and transistor 114 will againconduct and lock in the conducting condition until it is reset. Oncetransistor 114 is conducting and is locked, it is necessary to reset thesystem. This is accomplished by opening normally-closed switch'138 andthen closing it again. Also, contained within anti-tampering section 106is condensor 140. Condensor 140 acts to delay the operation of thesystem for a time sufficient to prevent false alarms.

6 The circuit of FIG. 3 can also include any or all of the testing andoperating switches of the system of FIG. 2, for example, line switch 34and testing switches 42 and 40.

In accordance with FIG. 4 of the drawings, the system of the presentinvention may be housed in a single housing for use with a wide varietyof devices. For example, it may be used as a protector for such items asbrief cases or display cases when ones attention is temporarilydiverted. Also, it could be used in exhibition booths to protectvaluable items when the attendant must step away for a moment. Inaccordance with FIG. 4, the motion-sensitive switch 142 is made up of aring type contact 144 and a vibrating arm 146 having a weight 148attached to the end thereof. In this particular instance, the powersource can be two 9 volt DC batteries 150. A loading component 152, ofproper value, is included and a conventional alarm 154. In thisinstance, the alarm 154 can be a Mallory Sonalann or equivalent. Forthis particular purpose, the system also includes a key-operated lineswitch or system switch 156. This switch will, or course, be necessarysince the system should not be activated unless a brief case or the likeis put in a stationary position. Obviously, the system could not beactivated while someone was carrying the brief case, since any motion,as previously dis cussed, will set off the alarm. Therefore,key-operated switch 156 is an essential component of the system asdescribed in FIG. 4.

It is thus apparent from the drawings that a simple, inexpensive andhighly effective alarm system is provided. The alarm "system includes asingle power source supplying both the switch and alarm sections and theintegrity or anti-tamper section of the alarm system. The switch sectionincludes a very sensitive switch which will set off the alarm on theslightest disturbance of the switch itself. On the other hand, if anintruder should locate the switch and make an effort to deactivate theswitch by cutting or pulling out the cord leading from the switch to thealarm section, this in and of itself causes an alarm condition, thusindicating that the line has been tampered with somewhere between theswitch and the alarm section.

In light of the above, it is obvious that the system of the presentinvention provides a simple, inexpensive and sensitive alarm system foralerting the user of the intrusion onto or into property or thedisturbance of objects to be protected. The sensor or switch unit can bereadily attached to any appropriate piece of equipment or object andthus indicate any movement of the object. For example, the unit isparticularly suitable for use on a boat, the motor of a boat, amotorcycle, an open vehicle, such as a jeep or a truck, a car, a camperor trailer, a show vehicle or any item located in a remote, unprotectedarea. For example, the sensor unit may be attached to the underside ofthe hood of a vehicle, to the door of a vehicle, to the door or gate ofan enclosed area or any other appropriate place where an intruder willobviously move some element or part of the object being protected or adoor or gate to the area to be protected. This area can be remotelylocated as indicated since the electrical line from the sensor or switchunit then passes to another location where the user can observe or hearthe alarm. The alarm and antitamper section as well as the power sectionof the device is therefore located where the user wishes. If an intruderin any way disturbs the object or area being protected, the slightestmovement of the sensor unit will cause the alarm to be set off.Similarly, should the in-' truder discover the line from the switch orsensor unit to the area where the user is located and decide to eitherbreak or cut the line, such breaking or cutting of the line will alsoset off the alarm by virtue of the completion of the second circuitthrough the buzzer and through the second switch located adjacent thepower supply and alarm unit.

It is obvious that certain variations of the system can be made withoutaltering the basic concepts involved, For example, a conventionalholding or latching relay can be inserted in the alarm circuit so that asingle contact between contacts 20 and 24 of switch will cause the relayto close and latch and thus continuously sound the buzzer or alarm.Thus, once contact is made, the sounding of the buzzer or alarm will notdepend upon whether contact is made a second or third time by thecontacts of switch 10. Similarly, the AC power supply can be substitutedby a suitable DC power supply. However, it should be clearly recognizedat this point that a single buzzer or alarm and a single source of powerare operative for both the anti-intrusion or switch section of thesystem as well as the anti-tamper section of the system. Thus, a singlealarm and a single power source operate and create an alarm conditionwhether the switch section is operating normally or whether the switchsection has been disconnected by one tampering with the line leadingfrom the switch section to the alarm and control section of the alarmsystem.

We claim:

1. An anti-intrusion alarm system, consisting of; a power andanti-tampering unit, including a source of power, alarm means and anormally-closed switch means including holding means for holding saidnormally-closed switch means open when said holding means is energized;a remotely located detector unit including a motion-sensitive switchmeans; and cable means connecting said power and anti-tampering unit tosaid detector unit, including a first conductor leading from one contactof said motion-sensitive switch to a series combination of said alarmmeans and a first terminal of said power source in said power andanti-tampering unit, a second conductor leading from a second terminalof said power source to a second contact of said motion-sensitiveswitch, to complete a first circuit through said power source and saidalarm means when said motion-sensitive switch is closed, and a thirdconductor leading from said second contact of said motion-sensitiveswitch to a series combination of said holding means and said firstterminal of said power source, to complete a second circuit to energizesaid holding means and hold said normally-closed switch open when saidfirst conductor and said third conductor are intact and to deenergizesaid holding means and permit said normally-closed switch to close whensaid first or said third conductor are cut; and a third circuit withinsaid power and anti-intrusion unit including said power source, saidalarm means and the contacts of said normally-closed switch, wherebysaid alarm means is energized when said holding means is deenergized andsaid normally-closed switch is closed.

2. A system in accordance with claim 1 wherein the normally-closedswitch means is the contacts of a normally-closed relay and the holdingmeans is the coil of said relay.

3. A system in accordance with claim 1 wherein the source of power is anAC'source of power.

4. A system in accordance with claim 3 wherein the source of powerincludes a step-down transformer adapted to reduce the voltage of the ACsource of power.

5. A system in accordance with claim 1 wherein the alarm means is amulti-vibrator.

6. A system in accordance with claim 1 wherein the motion-sensitiveswitch means includes a vertically-disposed hollow ring forming thesecond contact of said switch and a resilient, spring-type arm formingthe first contact of said switch, passing through the opening in thehollow ring contact and having a weight mounted on its free end.

7. A system in accordance with claim 6 wherein the resilience of the armand the magnitude of the weight are adjusted such that slight verticalmovement of the switch means will cause the arm contact to vibrateagainst the edges of the ring contact and turning of the switch oneither side or on its top will cause said arm contact to contact oneside or the top, respectively, of said ring contact.

8. A system in accordance with claim 1 wherein the first alarm circuitadditionally includes a test switch adapted to close a circuit bypassingthe switch means.

9. A system in accordance with claim 1 wherein the second alarm circuitincludes a test switch for interrupting the power to the holding means.

10. An anti-intrusion alarm system, consisting of; a power andanti-tampering unit, including a source of power, alarm means and anormally-conducting, solidstate switching means including holding meansfor rendering said normally-conducting switching means nonconductingwhen said holding means is energized; a remotely located detector unitincluding a motion-sensitive switch means; and cable means connectingsaid power and anti-tampering unit to said detector unit, including afirst conductor leading from one contact of said motion-sensitive switchmeans to a series combination of said alarm means and a first terminalof said power source in said power and anti-tampering unit, a secondconductor leading from a second terminal of said power source to asecond contact of said motionsensitive switch means, to render a firstcircuit through said power source and said alarm means conducting whensaid motion-sensitive switch means is closed, and a third conductorleading from said second contact of said motion-sensitive switch meansto a series combination of said holding means and said first terminal ofsaid power source, to complete a second circuit to energize said holdingmeans and render said normally-conducting switching means non-conductingwhen said first conductor and said third conductor are intact and todeenergize said holding means and permit said normally-conductingswitching means to conduct when said first and said third conductor arecut, and a third circuit within said power and anti-intrusion unitincluding said power source, said alarm means and the terminals of saidnormally-conducting switching means, whereby said alarm means isenergized when said holding means is deenergized and saidnormally-conducting switching means is conducting.

11. A system in accordance with claim 10 wherein the alarm means is awarble tone generator.

12. A system in accordance with claim 10 wherein the normally-conductingswitching means is an N-type base, field-effect transistor.

13. A system in accordance with claim 10 wherein the holding means is aPNP transistor normally having 10 15. A system in accordance with claim13 wherein the cutting of any line leading to the source of the bias onthe base of the PNP transistor interrupts the application of said biasto said transistor.

1. An anti-intrusion alarm system, consisting of; a power andanti-tampering unit, including a source of power, alarm means and anormally-closed switch means including holding means for holding saidnormally-closed switch means open when said holding means is energized;a remotely located detector unit including a motion-sensitive switchmeans; and cable means connecting said power and anti-tampering unit tosaid detector unit, including a first conductor leading from one contactof said motion-sensitive switch to a series combination of said alarmmeans and a first terminal of said power source in said power andanti-tampering unit, a second conductor leading from a second terminalof said power source to a second contact of said motion-sensitiveswitch, to complete a first circuit through said power source and saidalarm means when said motion-sensitive switch is closed, and a thirdconductor leading from said second contact of said motionsensitiveswitch to a series combination of said holding means and said firstterminal of said power source, to complete a second circuit to energizesaid holding means and hold said normally-closed switch open when saidfirst conductor and said third conductor are intact and to deenergizesaid holding means and permit said normally-closed switch to close whensaid first or said third conductor are cut; and a third circuit withinsaid power and anti-intrusion unit including said power source, saidalarm means and the contacts of said normally-closed switch, wherebysaid alarm means is energized when said holding means is deenergized andsaid normally-closed switch is closed.
 2. A system in accordance withclaim 1 wherein the normally-closed switch means is the contacts of anormally-closed relay and the holding means is the coil of said relay.3. A system in accordance with claim 1 wherein the source of power is anAC source of power.
 4. A system in accordance with claim 3 wherein thesource of power includes a step-down transformer adapted to reduce thevoltage of the AC source of power.
 5. A system in accordance with claim1 wherein the alarm means is a multi-vibrator.
 6. A system in accordancewith claim 1 wherein the motion-sensitive switch means includes avertically-disposed hollow ring forming the second contact of saidswitch and a resilient, spring-type arm forming the first contact ofsaid switch, passing through the opening in the hollow ring contact andhaving a weight mounted on its free end.
 7. A system in accordance withclaim 6 wherein the resilience of the arm and the magnitude of theweight are adjusted such that slight vertical movement of the switchmeans will cause the arm contact to vibrate against the edges of thering contact and turning of the switch on either side or on its top willcause said arm contact to contact one side or the top, respectively, ofsaid ring contact.
 8. A system in accordance with claim 1 wherein thefirsT alarm circuit additionally includes a test switch adapted to closea circuit bypassing the switch means.
 9. A system in accordance withclaim 1 wherein the second alarm circuit includes a test switch forinterrupting the power to the holding means.
 10. An anti-intrusion alarmsystem, consisting of; a power and anti-tampering unit, including asource of power, alarm means and a normally-conducting, solid-stateswitching means including holding means for rendering saidnormally-conducting switching means non-conducting when said holdingmeans is energized; a remotely located detector unit including amotion-sensitive switch means; and cable means connecting said power andanti-tampering unit to said detector unit, including a first conductorleading from one contact of said motion-sensitive switch means to aseries combination of said alarm means and a first terminal of saidpower source in said power and anti-tampering unit, a second conductorleading from a second terminal of said power source to a second contactof said motion-sensitive switch means, to render a first circuit throughsaid power source and said alarm means conducting when saidmotion-sensitive switch means is closed, and a third conductor leadingfrom said second contact of said motion-sensitive switch means to aseries combination of said holding means and said first terminal of saidpower source, to complete a second circuit to energize said holdingmeans and render said normally-conducting switching means non-conductingwhen said first conductor and said third conductor are intact and todeenergize said holding means and permit said normally-conductingswitching means to conduct when said first and said third conductor arecut, and a third circuit within said power and anti-intrusion unitincluding said power source, said alarm means and the terminals of saidnormally-conducting switching means, whereby said alarm means isenergized when said holding means is deenergized and saidnormally-conducting switching means is conducting.
 11. A system inaccordance with claim 10 wherein the alarm means is a warble tonegenerator.
 12. A system in accordance with claim 10 wherein thenormally-conducting switching means is an N-type base, field-effecttransistor.
 13. A system in accordance with claim 10 wherein the holdingmeans is a PNP transistor normally having a positive bias applied to itsbase.
 14. A system in accordance with claim 13 wherein themotion-sensitive switch means is mounted in the circuit in a positionsuch that closing said switch means shorts out the bias on the base ofthe PNP transistor.
 15. A system in accordance with claim 13 wherein thecutting of any line leading to the source of the bias on the base of thePNP transistor interrupts the application of said bias to saidtransistor.